As a conventional vibration power generating device, known is an electrostatic induction type vibration power generating device in which an electric charge is applied to one of electrodes of a variable capacity and the electric charge is induced to the other opposing electrodes via the electrostatic induction. The variation of capacity changes induced electric charge. The electrostatic induction type vibration power generating device generates electric power by extracting the change of the electric charge in the form of the electric energy (for example, see, Patent Literature 1).
FIG. 22 illustrates a schematic cross sectional view of a vibration power generator 10 disclosed in Patent Literature 1 (see, FIG. 4 and pages 10 to 11 of Patent Literature 1) as an example of a conventional electrostatic induction type vibration power generator using an electret material. The vibration power generator 10 is composed of a first substrate 11 provided with a plurality of conductive surface areas 13 and a second substrate 16 provided with a plurality of electret material areas 15. The first substrate 11 and the second substrate 16 are disposed so as to be spaced apart each other for a predetermined distance. The second substrate 16 including the electret material areas 15 is secured. The first substrate 11 including the conductive surface areas 13 is coupled to fixation structures 17 through springs 19. The springs 19 are connected to both side surfaces of the first substrate and further connected to the fixation structures 17. The first substrate 11 can be returned to (i.e., held by) a home position owing to the springs 19. Alternatively, the first substrate 11 can move laterally (e.g., can move horizontally in FIG. 22) to return to the home position. With the movement, an overlapped area between the electret material areas 15 and the opposing conductive surface areas 13 increases/decreases, resulting in changing electric charges of the conductive surface areas 13. The vibration power generator (i.e., electrostatic induction type vibration power generator) 10 generates electric power by extracting the change of the electric charges in the form of the electrical energy.